I am working with the LPC43S57 (running at 204 MHz) and am evaluating the external SDRAM performance. I am using the MT48LC4M32B2 128Mb*32 SDRAM from Micron.
To test the performance I use the gpdma_speed application from LPCOpen 3.01, using GDMA to make sure the application does not influence the transfer speed.
I modified the application to test different memory areas, including internal memory. I write 1 MB of data in chunks of 12 kB to the same 12 kB buffer, so it will fit in internal memory.
The results I see are a bit disappointing to me. Transfer from internal to internal memory is 80 MW/s (W = 32 bit), this is quite good. But transfer from external SDRAM to SDRAM is max 17 MW/s. How can I improve the speed of the SDRAM, to be closer to the internal speed? I would like to be able to execute from external SDRAM, but for that the speed should be better.
All measured results of 1MB transfer:
- Internal to internal: 80 MW/s
- External to external: 17 MW/s
- Internal to external: 50 MW/s
- External to internal: 26 MW/s
The configuration i use is:
static const IP_EMC_DYN_CONFIG_T MT48LC4M32_config =
{
/// Row refresh period.
EMC_NANOSECOND(64000000 / 4096),
/// Clock?
0x01,
/// tRP: Precharge Command Period. (ns)
EMC_NANOSECOND(18),
/// tRAS: Active to Precharge Command Period. (ns)
EMC_NANOSECOND(42),
/// tSREX: Self Refresh Exit Time. (ns), same as tXSR
EMC_NANOSECOND(67),
/// tAPR: Last Data Out to Active Time. (ns) ??
EMC_CLOCK(0x01),
/// tDAL: Data In to Active Command Time. (ns)
EMC_CLOCK(0x04),
/// tWR: Write Recovery Time. (ns)
EMC_NANOSECOND(12),
/// tRC: Active to Active Command Period. (ns)
EMC_NANOSECOND(60),
/// tRFC: Auto-refresh Period. (ns)
EMC_NANOSECOND(60),
/// tXSR: Exit Self Refresh. (ns)
EMC_NANOSECOND(67),
/// tRRD: Active Bank A to Active Bank B Time. (ns)
EMC_NANOSECOND(12),
/// tMRD Load Mode register command to Active command. (clocks)
EMC_CLOCK(0x02),
/// Device Configuration array.
{
{
/// For the Xenon board, EMC_DYCS0 is used.
EMC_ADDRESS_DYCS0,
/// RAS value.
2,
/// Mode Register value.
EMC_DYN_MODE_WBMODE_PROGRAMMED | EMC_DYN_MODE_OPMODE_STANDARD |
EMC_DYN_MODE_CAS_2 | EMC_DYN_MODE_BURST_TYPE_SEQUENTIAL |
EMC_DYN_MODE_BURST_LEN_4,
/// Dynamic Configuration value.
EMC_DYN_CONFIG_DATA_BUS_32 |
EMC_DYN_CONFIG_4Mx32_4BANKS_12ROWS_8COLS | EMC_DYN_CONFIG_MD_SDRAM
},
{0, 0, 0, 0},
{0, 0, 0, 0},
{0, 0, 0, 0}
}
};Regards,
Johan Borkhuis
